The invention relates to a dental x-ray diagnostic installation for producing panoramic tomograms of the jaw of a patient. The apparatus or installation includes a rotary unit which contains a carrier for supporting a radiation source and also supporting a film cassette holder for accepting film cassettes, an arrangement by which the carrier is adjustably rotated around a vertical axis and the axis is moved along an orbital curve corresponding to the dental arch of the patient. Another feature is that the film cassette holder or the film cassette insertable therein is adjustable, both so that teeth are successively imaged on the film together with the jaw and includes at least one detector arrangement adjacent to the film cassette which arrangement supplies electrical signals corresponding to a dose rate of radiation impinging thereon and provides a signal to a control for at least the tube voltage of the radiation source.
U.S. Pat. No. 4,021,672, which is based on German application No. 24 47 075 and whose disclosures are incorporated by reference, is an example of a known x-ray diagnostic installation or apparatus. In this known device, the head of the patient is held in a corresponding retension means. During the exposure, the x-ray source and film cassette holder move around the head of the patient. The carrier and the film cassette holder are thereby rotated around a vertical axis so that the x-rays always impinge on the jaw, or respectively the teeth, to be exposed at essentially a right angle so that the distance between the teeth and film remains essentially constant. As a consequence of the relative motion between the film cassette and the radiation source, the teeth are successively imaged on the film together with the jaw.
In accordance with the previous techniques, the exposure data or settings (kV, mA, sec) with which the radiation source is operated are visually and emperically determined by the user. For example, user will emperically identify in accordance with value pairs for the kV/mA prescribed by the manufacturer for various body sizes for a child, a youth, an adult, and extra large, and then the emperically identified value pairs are set into the apparatus.
It can be easily understood that such a selection of the exposure data undertaken in a purely visual way cannot always be optimum and assumes great experience on the part of the apparatus user or operator. Further, it is not possible, given the known apparatus, to produce a patient-related tomogram position or, respectively, this is possible only in an extremely complicated way.